1. Field of the Invention
This invention relates to an indexable inserted milling tool. More particularly, this invention relates to a milling cutter with tangentially mounted indexable cutting inserts.
2. Description of the Related Art
In the process of milling turbine blades or “buckets”, one generally finds in use solid carbide end mills (SCEM), inserted carbide end mills (ICEM), and insert face mills for roughing only. Ball nose end mills (solid and inserted) are used for semi-finishing and in some case, finishing. The cutter paths programmed are typically radial or axial with regard to the blade form. In either case, there are axes of rotation on both the blade and the cutter, with additional axes used to produce large concave and convex surfaces. The paths are followed for as long as it takes to reduce either a block of material or a near-net shaped forging to its intended size and shape. The type of cutting tool used is generally dictated by the condition of the workpiece at the start of the process, and the capabilities of the machine. In both cases, the semi-finishing and finishing cuts are addressed by smaller diameter tools due to the radii of the turbine blade surfaces.
Axial cutter paths have been used on several types of single and multi-spindle NC and CNC machines. The path is basically one that travels across the front and back sides of the blade with cutting taking place across an edge of the blade between the cutting of two sides. The path includes the convex and concave surfaces, which change rather quickly as the progression of the tool makes its way around the blade, and slowly progresses from one end of the blade to the other.
Basically, radial paths travel from root or base to tenon or blade tip until the front or back of the blade is cut to depth. The path then moves along the leading or trailing edge to cut to the desired depth, and continues to the uncut front or back of the blade to finish removing material in the same manner as the opposite. This process has traditionally been accomplished with what is called a “Hydrotel” machine, which uses a dovetail-shaped cutter with round inserts. These multi-spindle machines are quickly becoming antiquated, spending on maintenance and refurbishing is drastically reduced, and the owners are opting for new CNC machines. Lately, machinists have found that the radial cutting path is more cost effective, and the ability to reduce or eliminate secondary finishing operations is obtainable with creative programming and tooling. This includes, but is not limited to, the tilting of the milling machine's spindle, or the workpiece such that a ball-nosed tool will not cut with the surfaces of the tool that have minimal effective speeds and feeds.